Sensor module and method for correcting sense output signal therefrom

ABSTRACT

A sense signal outputted from a sensor element and a reference voltage having a constant voltage level are selectively inputted to an amplifier, and amplified signals thereof are sequentially outputted as A/D-converted data by an A/D converter. An average of a predetermined number of A/D-converted data corresponding to the reference voltage is calculated, and a correction value is obtained by subtracting the average from one of the A/D-converted data corresponding to the reference voltage. Corrected data is obtained by subtracting the correction value from each A/D-converted data corresponding to the sense signal outputted from the sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sensor module including a sensorelement, an amplifier and an analog to digital (A/D) converter.

2. Description of the Related Art

Various sensors including an acceleration sensor, an angular velocitysensor, etc., a differential amplifier for amplifying sense signalsoutputted from those sensors, and an A/D converter for A/D-convertingthe amplified sense signals are packaged into one sensor module, whichis well known to those skilled in the art. This sensor module can bereadily incorporated into another device, and contribute to reducing thenumber of components of the device and miniaturizing the device.

As a technique for increasing precision of an output signal in anapparatus using a sensor, in Japanese Patent Laid-open Publication No.H9-43264 is disclosed an acceleration detection apparatus which has anacceleration sensor for obtaining an output signal corresponding to anacceleration in a traveling direction of an automobile. Thisacceleration detection apparatus comprises means for retaining, as acorrection signal, the output signal from the acceleration sensor whenthe number of engine rotations of the automobile is constant, namely,the acceleration in the traveling direction of the automobile is 0, andthereafter removing the correction signal from the output signal fromthe acceleration sensor. The correction signal includes unnecessarycomponents not related to the acceleration in the traveling direction ofthe automobile, such as a drift component occurring in the output signalfrom the acceleration sensor due to a temperature variation or otherenvironmental variations, or a gravitational acceleration componentapplied to the acceleration sensor when the automobile travels on anuphill road. These unnecessary components are removed by the removingmeans. Therefore, this acceleration detection apparatus can reduce anerror which will occur due to such unnecessary components.

SUMMARY OF THE INVENTION

A sensor module always suffers what is called a fluctuation in a senseoutput signal resulting from the fact that an output signal from acomponent other than a sensor, namely, an operational amplifier or A/Dconverter varies due to a certain factor. That is, a fluctuationcomponent is ceaselessly introduced into a sense output signal finallyoutputted from the sensor module, thereby making it difficult to obtainthe sense output signal with high precision.

An object of the present invention is to provide a sensor moduleincluding various sensors, a differential amplifier, an A/D converter,etc., which is capable of removing a fluctuation component resultingfrom an output variation in a signal processor provided downstream ofthe sensors, such as the differential amplifier or A/D converter, andobtaining a higher precision of sense output signal, and a method forcorrecting the sense output signal from the sensor module.

In accordance with an aspect of the present invention, the above andother objects can be accomplished by the provision of a sensor modulecomprising a sensor element for generating a sense signal correspondingto a sensed amount, an amplifier for amplifying the sense signal andoutputting the amplified signal, and an analog to digital (A/D)converter for sequentially A/D-converting the amplified signal with apredetermined timing to obtain A/D-converted data, and sequentiallyoutputting the obtained A/D-converted data, wherein the sensor modulefurther comprises: reference voltage generation portion for generating areference voltage having a constant voltage level; an input signalselection portion for selectively supplying either one of the sensesignal and reference voltage to the amplifier; an averaging portion forcalculating an average of a predetermined number of A/D-converted datacorresponding to the reference voltage; a correction value generationportion for subtracting the average from one of the A/D-converted datacorresponding to the reference voltage and outputting a result of thesubtraction as a correction value; and a correction portion forsubtracting the correction value from each A/D-converted datacorresponding to the sense signal to obtain corrected data, andoutputting the obtained corrected data as a sense output signal.

In accordance with another aspect of the present invention, there isprovided a method for correcting a sense output signal from a sensormodule, the sensor module including a sensor element for generating asense signal corresponding to a sensed amount, an amplifier foramplifying the sense signal and outputting the amplified signal, and anA/D converter for sequentially A/D-converting the amplified signal witha predetermined timing to obtain A/D-converted data, and sequentiallyoutputting the obtained A/D-converted data, the method comprising:inputting a reference voltage having a constant voltage level to theamplifier and obtaining an average of a predetermined number ofA/D-converted data corresponding to the reference voltage; subtractingthe average from one of the A/D-converted data corresponding to thereference voltage to obtain a correction value; and inputting the sensesignal to the amplifier, subtracting the correction value from eachA/D-converted data corresponding to the sense signal to obtain correcteddata, and outputting the obtained corrected data as the sense outputsignal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

FIG. 1 is a block diagram showing the configuration of a sensor moduleaccording to an exemplary embodiment of the present invention;

FIG. 2 is a view illustrating an initialization operation of the sensormodule according to the present embodiment;

FIG. 3 is a view illustrating a sensing operation of the sensor moduleaccording to the present embodiment;

FIG. 4A is a graph illustrating a transition of a sense output signalfrom the sensor module according to the present embodiment;

FIG. 4B is a graph illustrating a transition of a sense output signalfrom a conventional sensor module; and

FIG. 4C is a table illustrating a comparison between standard deviationsof the sense output signal from the sensor module according to thepresent embodiment and the sense output signal from the conventionalsensor module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be described inconjunction with the annexed drawings. FIG. 1 is a block diagram showingthe configuration of a sensor module according to an exemplaryembodiment of the present invention. A sensor 10 may be, for example, apiezoresistor-type three-axis acceleration sensor. Thepiezoresistor-type acceleration sensor has a structure consisting of aframe, mass and beam which are formed from silicon as a base materialusing a micro electro-mechanical system (MEMS) technique, in whichpiezoresistors are disposed on the beam. A piezoresistor is an elementwhose resistance varies due to a variation in the number of carriers ormobility in a semiconductor crystal lattice when an external mechanicalforce is applied to the crystal lattice so as to deform it. When anacceleration is applied to a sensor chip, the mass moves and deformationoccurs on the beam. Stress occurs in the piezoresistors on the beam dueto the deformation, resulting in a variation in resistance. In thepiezoresistor-type acceleration sensor, a bridge circuit is formed withthe piezoresistors to output the variation in the resistance of thepiezoresistors as an electrical signal. That is, a sense voltage Vshaving a voltage level corresponding to the acceleration applied to thesensor element is generated between output terminals of the sensor 10.

A reference voltage generator 11 is a direct current (DC) voltagegeneration circuit that generates a reference voltage Vref having aconstant voltage level between output terminals thereof. The referencevoltage generator 11 may be implemented with, for example, a bandgapcircuit, etc. such that the reference voltage Vref can always bemaintained at a stable DC voltage level, not dependent on an ambienttemperature or supply voltage.

An input switching circuit 12 is a switching circuit that switches aninput voltage to a differential amplifier 13. To this end, the inputswitching circuit 12 includes a first switch SW1 a for switching theinput/cutoff of the sense voltage Vs from the sensor 10 to thedifferential amplifier 13, and a second switch SW2 a for switching theinput/cutoff of the reference voltage Vref from the reference voltagegenerator 11 to the differential amplifier 13. The switching of eachswitch is carried out based on a control signal supplied from a controlcircuit 15.

The differential amplifier 13 has two input terminals, and amplifies andoutputs a difference between voltages applied to the two inputterminals. The sense voltage Vs supplied from the sensor 10 or thereference voltage Vref supplied from the reference voltage generator 11is outputted as a signal amplified by a predetermined amplificationfactor by the differential amplifier 13. The reason why the signalamplification is performed using the differential amplifier 13 in thismanner is that the sense voltage Vs from the sensor 10 is weak and thusneeds to be raised to a voltage level required for A/D conversionthereof. Also, because the differential amplifier 13 amplifies adifference between signals at the input terminals thereof, even thoughnoise is introduced into the signals, it hardly matters in that it isdifficult to appear as an electrical signal difference.

An A/D converter 14 samples the amplified signal of the sense voltage Vsor reference voltage Vref supplied from the differential amplifier 13 ata predetermined period to convert the amplified signal into a digitalamount corresponding to the magnitude thereof, and sequentially outputsthe converted digital amount as A/D-converted data. The A/D converter 14may be, for example, a known consecutive comparison type A/D converter,and samples and holds the amplified signal of the sense voltage Vs orreference voltage Vref supplied from the differential amplifier 13,converts the sampled and held signal into a digital amount whileperforming comparison beginning with a most significant bit, andsequentially outputs the converted digital amount.

An output switching circuit 16 includes a first switch SW1 b and asecond switch SW2 b, each of which is turned on/off based on a controlsignal supplied from the control circuit 15. With this configuration,A/D-converted data A(x) corresponding to the sense voltage Vs from thesensor 10, sequentially outputted from the A/D converter 14, isoutputted from an output terminal Q1 through the first switch SW1 b, andA/D-converted data D(x) corresponding to the reference voltage Vref fromthe reference voltage generator 11, sequentially outputted from the A/Dconverter 14, is outputted from an output terminal Q2 through the secondswitch SW2 b.

The control circuit 15 supplies control signals to the input switchingcircuit 12 and the output switching circuit 16 to control ON/OFF of eachswitch of the input switching circuit 12 so as to alternately supply thesense voltage Vs and the reference voltage Vref to the differentialamplifier 13 with a predetermined timing, and to synchronize an ON/OFFtiming of the first and second switches of the output switching circuit16 with an ON/OFF timing of the first and second switches of the inputswitching circuit 12 so as to bisect output sources of an A/D-convertedoutput of the sense voltage Vs and an A/D-converted output of thereference voltage Vref, as stated above. That is, the control circuit 15operatively associates the ON/OFF timing of the output switching circuit16 with the ON/OFF timing of the input switching circuit 12 such that anA/D-converted output corresponding to the sense voltage Vs from thesensor 10 is outputted from the output terminal Q1 through the firstswitch SW1 b and an A/D-converted output corresponding to the referencevoltage Vref from the reference voltage generator 11 is outputted fromthe output terminal Q2 through the second switch SW2 b.

A memory 17 is a storage medium for storing some of the A/D-converteddata D(x) corresponding to the reference voltage Vref, sequentiallysupplied through the second switch SW2 b of the output switching circuit16. In an initialization operation upon power-on to be described later,the memory 17 stores, for example, 100 sampled data, among theA/D-converted data corresponding to the reference voltage Vref,sequentially supplied.

An averaging circuit 18 calculates an average Dave of the A/D-converteddata of the reference voltage Vref stored in the memory 17 and retainsthe calculated average.

A hold circuit 19 holds one A/D-converted data D included in theA/D-converted data D(x) corresponding to the reference voltage Vref,sequentially supplied through the second switch SW2 b of the outputswitching circuit 16, based on a control signal and outputs the helddata.

A first subtracter 20 subtracts the average Dave retained by theaveraging circuit 18 from the A/D-converted data D of the referencevoltage Vref held by the hold circuit 19 and outputs a result of thesubtraction as a correction value E (=D−D_(ave)).

A second subtracter 21 subtracts the subtraction result of the firstsubtracter 20, or the correction value E, from the A/D-converted dataA(x) corresponding to the sense voltage Vs from the sensor 10,sequentially supplied through the first switch SW1 b of the outputswitching circuit 16, and outputs a result of the subtraction ascorrected data M(x) (=A(x)−E). This corrected data M(x) is a final senseoutput signal from the sensor module of the present invention.

Next, the operation of the sensor module with the above-statedconfiguration according to the present embodiment will be described withreference to FIGS. 2 and 3. FIGS. 2 and 3 are timing charts illustratingthe operations of the respective functional blocks constituting thesensor module. FIG. 2 illustrates an initialization operation of thesensor module when the sensor module is powered on, and FIG. 3illustrates an acceleration sensing operation of the sensor module.

First, the initialization operation of the sensor module will bedescribed with reference to FIG. 2. Upon application of power to thesensor module, the initialization operation of the sensor module isstarted. In this initialization operation, the averaging circuit 18calculates an average of the reference voltage Vref outputted from thereference voltage generator 11 within a certain period and retains thecalculated average. That is, upon application of power to the sensormodule, the control circuit 15 supplies control signals to the inputswitching circuit 12 and the output switching circuit 16 to turn off thefirst switch SW1 a of the input switching circuit 12 and turn on thesecond switch SW2 a thereof and turn off the first switch SW1 b of theoutput switching circuit 16 and turn on the second switch SW2 b thereof(S1). As a result, the reference voltage Vref generated between theoutput terminals of the reference voltage generator 11 is applied to thedifferential amplifier 13. Then, the differential amplifier 13 generatesan amplified signal by amplifying the reference voltage Vref by apredetermined amplification factor, and supplies the generated amplifiedsignal to the A/D converter 14.

The A/D converter 14 samples the amplified signal of the referencevoltage Vref supplied thereto at a predetermined sampling period andsequentially outputs the sampled signal as A/D-converted data D(x) (S2).Also, the A/D-converted data D(x) is superimposed by a fluctuationcomponent as the input voltage is passed through the differentialamplifier 13 and the A/D converter 14.

The A/D-converted data D(x) corresponding to the reference voltage Vref,sequentially outputted from the A/D converter 14, is supplied to thememory 17 through the second switch SW2 b of the output switchingcircuit 16. The memory 17 stores for example, 100 data, among theA/D-converted data of the reference voltage Vref periodically suppliedcorrespondingly to the sampling period of the A/D converter 14 (S3).Also, the data stored in the memory 17 is retained therein until thesensor module is powered off.

The averaging circuit 18 extracts the 100 data stored in the memory 17,calculates an average Dave of the extracted data and retains thecalculated average (S4). A fluctuation component can be offset byaveraging a plurality of A/D-converted data superimposed by thefluctuation component by means of the averaging circuit 18. That is, theaverage Dave calculated by the averaging circuit 18 is defined as a truevalue of the reference voltage Vref after amplification from which thefluctuation component was removed, and is used to extract thefluctuation component in the sensing operation of the sensor module ofthe present invention to be described below. When the calculation of theaverage Dave is completed, the initialization operation is ended.

Also, the average D_(ave) is calculated when a normal calibrationtemperature of the sensor is measured (when a sensitivity offset valueof the sensor is acquired), and then stored in a nonvolatile memory orthe like. Therefore, it is also possible to correct a variation in thereference voltage Vref resulting from a temperature variation withoutcarrying out the measurement again upon application of power.

Next, the acceleration sensing operation of the sensor module aftercompletion of the initialization operation will be described withreference to FIG. 3. The control circuit 15 supplies control signals tothe input switching circuit 12 and the output switching circuit 16 toturn off the first switch SW1 a of the input switching circuit 12 andturn on the second switch SW2 a thereof and turn off the first switchSW1 b of the output switching circuit 16 and turn on the second switchSW2 b thereof (S11). As a result, the reference voltage Vref generatedbetween the output terminals of the reference voltage generator 11 isapplied to the differential amplifier 13. Then, the differentialamplifier 13 generates an amplified signal by amplifying the referencevoltage Vref by a predetermined amplification factor, and supplies thegenerated amplified signal to the A/D converter 14. The A/D converter 14samples the amplified signal of the reference voltage Vref suppliedthereto at a predetermined sampling period and sequentially outputs thesampled signal as A/D-converted data D(x) (S12). The A/D-converted dataD(x) is superimposed by a fluctuation component as the input voltage ispassed through the differential amplifier 13 and the A/D converter 14.The A/D-converted data D(x) corresponding to the reference voltage Vref,outputted from the A/D converter 14, is supplied to the hold circuit 19through the second switch SW2 b of the output switching circuit 16. Thehold circuit 19 holds one data D1 included in the A/D-converted dataD(x) sequentially supplied thereto with a timing based on a controlsignal and outputs the held data (S13). The A/D-converted data D1 heldby the hold circuit 19 is supplied to the first subtracter 20. The firstsubtracter 20 subtracts the average Dave acquired in the initializationoperation from the A/D-converted data D1 and outputs a result of thesubtraction as a correction value E1 (=D1−D_(ave)) (S14). That is,because the average Dave is a true value of the reference voltage Vreffrom which the fluctuation component was removed, as stated previously,and D1 is A/D-converted data of the reference voltage Vref including thefluctuation component, it is possible to extract only the fluctuationcomponent by subtracting D_(ave) from D1. Namely, the correction valueE1 outputted from the first subtracter 10 represents the magnitude ofthe fluctuation component at a data D1 acquisition time. Also, becausethe data stored in the memory 17 and the average Dave of the averagingcircuit 18 are those set and retained in the initialization step, theyare not changed in the acceleration sensing operation.

Then, the control circuit 15 supplies control signals to the inputswitching circuit 12 and the output switching circuit 16 to turn on thefirst switch SW1 a of the input switching circuit 12 and turn off thesecond switch SW2 a thereof and turn on the first switch SW1 b of theoutput switching circuit 16 and turn off the second switch SW2 b thereof(S15). As a result, the sense voltage Vs generated between the outputterminals of the sensor 10 is applied to the differential amplifier 13.Then, the differential amplifier 13 generates an amplified signal byamplifying the sense voltage Vs by a predetermined amplification factor,and supplies the generated amplified signal to the A/D converter 14. TheA/D converter 14 samples the amplified signal of the sense voltage Vssupplied thereto at a predetermined sampling period and sequentiallyoutputs the sampled signal as A/D-converted data A(x) (S16). Also, theA/D-converted data A(x) is superimposed by a fluctuation component asthe input voltage is passed through the differential amplifier 13 andthe A/D converter 14. The A/D-converted data A(x) corresponding to thesense voltage Vs from the sensor 10, outputted from the A/D converter14, is sequentially supplied to the second subtracter 21 through thefirst switch SW1 b of the output switching circuit 16. The secondsubtracter 21 subtracts the correction value El (=D1−D_(ave)) outputtedfrom the first subtracter 20 from each of the A/D-converted data of thesense voltage Vs sequentially supplied thereto and outputs a result ofthe subtraction as corrected data M(x) (=A(x)−E1) (S17). As statedabove, the correction value E1 supplied from the first subtracter 10represents the magnitude of the fluctuation component at the data D1acquisition time. The subtracter 21 removes the fluctuation component bysubtracting the correction value E1 from each of the A/D-converted dataof the sense voltage Vs superimposed by the fluctuation component. Inthis manner, the fluctuation correction is carried out with respect tothe sense output signal.

Because the fluctuation component always varies in magnitude, thecorrection value acquisition and correction process is carried out atintervals of a predetermined period. That is, after acquiring apredetermined number of A/D-converted data of the sense voltage Vs fromthe sensor 10, the control circuit 15 again supplies control signals tothe input switching circuit 12 and the output switching circuit 16 toturn off the first switch SW1 a of the input switching circuit 12 andturn on the second switch SW2 a thereof and turn off the first switchSW1 b of the output switching circuit 16 and turn on the second switchSW2 b thereof (S18). As a result, the reference voltage Vref is againapplied to the differential amplifier 13. The A/D converter 14 convertsan amplified signal of the reference voltage Vref supplied thereto intoA/D-converted data D(x) (S19) and supplies the A/D-converted data to thehold circuit 19 through the output switching circuit 16. The holdcircuit 19 holds one data D2 included in the new A/D-converted data D(x)sequentially supplied thereto with a timing based on a control signaland outputs the held data (S20). The first subtracter 20 subtracts theaverage D_(ave) from the A/D-converted data D2 held by the hold circuit19 and outputs a result of the subtraction as a new correction value E2(=D2−D_(ave)) (S21). The new correction value E2 represents themagnitude of the fluctuation component at a data D2 acquisition time.The correction value may be updated one after another.

Then, the control circuit 15 controls the input switching circuit 12 andthe output switching circuit 16 to operate in synchronism. Specifically,the control circuit 15 supplies control signals to the input switchingcircuit 12 and the output switching circuit 16 to turn on the firstswitch SW1 a of the input switching circuit 12 and turn off the secondswitch SW2 a thereof and turn on the first switch SW1 b of the outputswitching circuit 16 and turn off the second switch SW2 b thereof (S22).As a result, new A/D-converted data A(x) corresponding to the sensevoltage Vs from the sensor 10 is obtained (S23). The second subtracter21 subtracts the new correction value E2 from each of the newA/D-converted data A(x) sequentially supplied thereto, so as to output,as the sense output signal, corrected data M(x) from which thefluctuation component occurring in the new period was removed (S24).

As described above, in the initialization operation, the sensor moduleof the present invention passes a reference voltage Vref having aconstant voltage level through the differential amplifier 13 and the A/Dconverter 14 to acquire A/D-converted data superimposed by a fluctuationcomponent, and averages the acquired A/D-converted data to obtain anaverage D_(ave) corresponding to a true value of the reference voltageVref from which the fluctuation component was offset. In the sensingoperation, the sensor module of the present invention specifies thefluctuation component by subtracting the average D_(ave) fromA/D-converted data D corresponding to the reference voltage Vref at acertain time. Then, the sensor module corrects the output of the sensorby subtracting the fluctuation component from each A/D-converted datacorresponding to the sensor output, and outputs the correction result asa final sense output signal. Therefore, it is possible to eliminate theeffect of the fluctuation component and obtain a high precision of senseoutput signal. Also, because the extraction of the fluctuationcomponent, namely, the acquisition of the correction value isperiodically performed as stated above, it is possible to properlyperform the correction with respect to the fluctuation component alwaysvarying. Further, it is preferable that a period in which the referencevoltage generator 11 is connected to the differential amplifier 13 foracquisition of the correction value E is as short as possible.

FIG. 4A is a graph illustrating a transition of a sense output signalfrom the sensor module of the present invention under the condition thatan acceleration is 0, which plots a moving average of 100 data measuredfor 22 hours. FIG. 4B is a graph illustrating, as a comparative example,a transition of a sense output signal from a conventional sensor modulewith no fluctuation correction function under the same condition. Also,a broken line shown in each graph represents an ideal value of the senseoutput signal. As apparent from comparison between the two graphs, itcan be seen that an output variation from the ideal value issignificantly reduced by performing fluctuation correction with respectto the sense output signal. FIG. 4C illustrates standard deviations ofthe two sense output signals. It can be understood from FIG. 4C that thedeviation of the sense output signal, namely, the fluctuation componentsuperimposing the sense output signal is reduced by almost half owing tothe effect of the fluctuation correction.

Also, although the sensor 10 has been described for illustrativepurposes in the above embodiment to be an acceleration sensor, it isapplicable to all sensors including an angular velocity sensor,temperature sensor, magnetometric sensor, pressure sensor, etc. Also,the A/D converter 14 is not limited to a consecutive comparison type A/Dconverter, but may be an A/D converter of any other type such as acharge equilibration type or dual integral type. In addition, althoughthe sensor module has been described in the above embodiment to acquireA/D-converted data of a reference voltage Vref, specify a fluctuationcomponent based on the acquired A/D-converted data, and then receive theoutput of the sensor and subtract the fluctuation component from thereceived sensor output, it may receive and retain the sensor output inadvance, and then specify the fluctuation component and subtract thefluctuation component from the retained sensor output.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

The invention has been described with reference to the preferredembodiments thereof. It should be understood by those skilled in the artthat a variety of alterations and modifications may be made from theembodiments described above. It is therefore contemplated that theappended claims encompass all such alterations and modifications.

This application is based on Japanese Patent Application No. 2008-065446which is hereby incorporated by reference.

1. A sensor module including a sensor element for generating a sensesignal corresponding to a sensed amount, an amplifier for amplifying thesense signal and outputting the amplified signal, and an analog todigital (A/D) converter for sequentially A/D-converting the amplifiedsignal with a predetermined timing to obtain A/D-converted data, andsequentially outputting the obtained A/D-converted data, the sensormodule comprising: a reference voltage generation portion for generatinga reference voltage having a constant voltage level; an input signalselection portion for selectively supplying either one of the sensesignal and reference voltage to the amplifier; an averaging portion forcalculating an average of a predetermined number of A/D-converted datacorresponding to the reference voltage; a correction value generationportion for subtracting the average from one of the A/D-converted datacorresponding to the reference voltage and outputting a result of thesubtraction as a correction value; and a correction portion forsubtracting the correction value from each A/D-converted datacorresponding to the sense signal to obtain corrected data, andoutputting the obtained corrected data as a sense output signal.
 2. Thesensor module according to claim 1, wherein the input signal selectionportion comprises an input switching circuit including a first switchfor switching supply and cutoff of the sense signal to the amplifier,and a second switch for switching supply and cutoff of the referencevoltage to the amplifier.
 3. The sensor module according to claim 1,further comprising an output switching circuit; wherein: the correctionportion includes a first subtracter for subtracting the correction valuefrom each A/D-converted data corresponding to the sense signal; theaveraging portion includes a memory for storing the predetermined numberof A/D-converted data corresponding to the reference voltage and anaveraging circuit for performing averaging of stored A/D-converted datain the memory; the correction value generation portion includes a secondsubtracter for subtracting the average from one of the A/D-converteddata corresponding to the reference voltage; and the output switchingcircuit includes a third switch for switching supply and cutoff of theA/D-converted data corresponding to the sense signal to the firstsubtracter, and a fourth switch for switching supply and cutoff of theA/D-converted data corresponding to the reference voltage to the memoryand the second subtracter.
 4. The sensor module according to claim 3,wherein the third switch and the fourth switch are alternately switchedon and off.
 5. The sensor module according to claim 4, furthercomprising a controller for controlling the input switching circuit andthe output switching circuit to operate in synchronism.
 6. A method forcorrecting a sense output signal from a sensor module, the sensor moduleincluding a sensor element for generating a sense signal correspondingto a sensed amount, an amplifier for amplifying the sense signal andoutputting the amplified signal, and an A/D converter for sequentiallyA/D-converting the amplified signal with a predetermined timing toobtain A/D-converted data, and sequentially outputting the obtainedA/D-converted data, the method comprising: inputting a reference voltagehaving a constant voltage level to the amplifier and obtaining anaverage of a predetermined number of A/D-converted data corresponding tothe reference voltage; subtracting the average from one of theA/D-converted data corresponding to the reference voltage to obtain acorrection value; and inputting the sense signal to the amplifier,subtracting the correction value from each A/D-converted datacorresponding to the sense signal to obtain corrected data, andoutputting the obtained corrected data as the sense output signal. 7.The method according to claim 6, wherein the correction value iscalculated at intervals of a predetermined period.
 8. The methodaccording to claim 6, wherein the correction value is updated one afteranother.